Interpretive Summary: Foodstuffs contaminated with pathogenic bacteria cause serious foodborne illness in humans. Salmonella is a pathogenic bacteria that is prevalent in the environment and lives in the gut of food producing animals. One problem scientists face in the control of Salmonella in animals is our lack of understanding about how Salmonella survives in these environments. In order to control pathogens such as Salmonella in the gut of animals, more information is needed on how pathogens live there. With a more complete understanding of the interactions between normal gut bacteria and pathogens, strategies can be developed to control the pathogens. Because the gut is complex and several hundred types of normal bacteria are present, studying the interactions between Salmonella and normal gut bacteria is very difficult. To better understand how Salmonella interacts with normal gut bacteria, we developed a simple model of the chicken gut. Using this model we studied the interactions between normal bacteria and Salmonella. We compared our findings with results from similar experiments in live chickens and found that our model gave comparable data. For example, killing of Salmonella in the model was similar to that observed in adult chickens. The results of this experiment are important because this model will allow scientists to perform studies directed towards understanding the interactions between pathogens and the normal gut bacteria. Through this understanding scientists will be able to develop new intervention strategies to stop the growth of pathogens in food- producing animals.

Technical Abstract:
An anaerobic continuous-culture of normal avian microflora obtained from adult birds was used to model the survivability of Salmonella typhimurium (ST) in the avian cecae. The continuous culture contained 29-different bacterial isolates from 10-different genera. When the continuous-culture was challenged with ST at concentrations between 10**1 and 10**5 log10 CFU the pathogen was unable to survive within the culture. When challenged with 10**6 CFU ST, the number of Salmonella CFU decreased to 10**2 within 5 days, however ST was not cleared from the culture and remained at a concentration of 10**2 for 65 days at which time the fermentation was terminated. When chicks were provided the continuous-culture on day-of- hatch, then challenged with ST two days later with up to 10**4 CFU Salmonella, no cecal colonization was observed 5-days after challenge. However, chicks challenged with 10**6 CFU Salmonella averaged 10**2 ST in cecal contents five days later. Chicks provided the continuous-culture on day-of-hatch and challenged with 10**2 or 10**4 CFU Salmonella had significantly (P<.05) fewer cecal Salmonella compared to untreated chicks. Salmonella challenge did not effect chick cecal or continuous-culture fermentation parameters and fermentation parameters within the continuous- culture and chick cecae were similar. Based upon similar fermentation parameters and Salmonella colonization levels it appears that this anaerobic continuous-culture of cecal bacteria is an excellent model of the cecae of chickens, and may serve as a valuable tool that can be used to better understand the interactions between Salmonella and normal avian flora in the cecae, which is the primary reservoir of Salmonella in commercial poultry.